Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$42.37	8.697%	$46.0549	$46.05	$46.05	$46.10
Purchase #2	$158.61	13.236%	$179.6036	$179.60	$179.60	$179.60
Purchase #3	$85.64	12.415%	$96.2722	$96.27	$96.25	$96.30
Purchase #4	$233.55	7.771%	$251.6992	$251.70	$251.70	$251.70
Purchase #5	$235.87	3.467%	$244.0476	$244.05	$244.05	$244.00
Purchase #6	$62.71	7.790%	$67.5951	$67.60	$67.60	$67.60
Purchase #7	$121.90	10.134%	$134.2533	$134.25	$134.25	$134.30
7 purchase totals =	$940.65		$1,019.5259	$1,019.52	$1,019.50	$1,019.60